The present disclosure relates to a development device including an antiscattering member for developer and an image forming apparatus including the development device.
In an image forming apparatus, such as an electrographic copying machine and a printer, an electrostatic latent image formed on a photosensitive drum is developed with toner (developer) by a developing roller provided in a development device. The development device is provided with an opening in a housing in which the developing roller is installed, and a rotation face of the developing roller is partially exposed outside the development device (a side of the photosensitive drum) through the opening.
The development device may be configured as a CRU (Customer Replaceable Unit) being attachable/detachable (connectable/disconnectable) to/from the image forming apparatus. The development device is provided with a structure in which the developing roller is exposed when the development device is completely attached to the image forming apparatus, while the developing roller is housed inside the housing when the development device is detached from the image forming apparatus. This structure prevents, in the connection and disconnection process of the development device, the developing roller from contacting with the photosensitive drum and protects the developing roller during shipping or storing of the development device.
When the developing roller and photosensitive drum perform rotational movement for developing, co-rotating airflow is generated on the surfaces of the developing roller and photosensitive drum by viscosity of air. Therefore, in particular, in a case where an amount of charge of toner is low due to high-humidity environment or the like, or another case where a magnetic brush receives air resistance, the toner not being contributed to the developing is scattered. Such scatter of the toner results in negative effects such as that an inside of the device is contaminated and the toner is unnecessarily accumulated and moved to the photosensitive drum, thereby causing image defects.
In order to prevent these negative effects, the development device may include a toner antiscattering member. The development device includes, for example, a toner regulating member, which is configured to regulate an amount of the toner carried by the developing roller, in one edge part of the opening in the housing (in an upstream side in a rotational direction of the developing roller), and a toner antiscattering member in another edge part (in a downstream side in the rotational direction of the developing roller). The toner antiscattering member is preferably provided adjacent to the developing roller so as not to scatter toner from the opening to an outside of the development device. The toner antiscattering member is also preferably provided near the above-mentioned other edge part so as to minimize a gap of the opening in order to restrain the scatter of the toner. For example, the toner antiscattering member is suspended from the other edge part or attached to a ceiling or an inside wall positioned at an internal side from the other edge part in the housing.
Further, in another example of the development device, the toner antiscattering member may be provided on an upstream side of the developing roller from a toner regulating blade, a distal end and the periphery to the toner antiscattering member is optionally curved and brought into contact with the developing roller on the tangent line of the developing roller. Therefore, with use of the toner antiscattering member, it is possible to restrain scatter of smoke of the toner generated in thinning a toner layer, without any disturbance in a thin layer of the toner, and to prevent a charge wire in a charger from being contaminated by the toner.
Furthermore, in a further example of the development device, the image forming device adopts a revolving development device and includes a shielding member (the toner antiscattering member) adjacent to the opening of the development device and at the outside thereof. Upper and lower sides of a developing area formed by a developing sleeve and a photosensitive body are enclosed by upper and lower shutters of the shielding member, while a minimal gap is maintained to a surface of the photosensitive body. Therefore, even if a rotation of the developing sleeve and photosensitive body generates airflow in an area enclosed by the shielding member, airflow toward an inside of the development device is generated to collect the toner separated from the developing sleeve to the inside thereof, thereby restraining the scatter of the toner to the outside of the development device.
In the development device provided with the toner antiscattering member as mentioned above, scattered toner may be caught on the toner antiscattering member and accumulated thereon. If the accumulated toner drops inside the development device, a major problem is not caused. However, if the accumulated toner drops outside the development device from the opening, there are some problems that the toner is moved to the photosensitive drum, thereby causing image defects, and the inside of the image forming apparatus is contaminated. In particular, in a case where the toner antiscattering member is provided near the edge part of the opening in the housing, a possibility that the toner accumulated around the toner antiscattering member drops from the opening to the outside of the development device is increased.
In another example of the above mentioned development device, since the toner antiscattering member is brought into contact with the developing roller, there are adverse effects such as that the toner antiscattering member and developing roller are damaged by friction, that products caused by deterioration of the toner antiscattering member or bleeding adheres to the developing roller and that toner is accumulated onto the contact portion. If the toner antiscattering member is fixable, the toner antiscattering member is easily warped or deformed on the basis of changes in usage environments such as temperature and humidity. When this toner antiscattering member comes in contact with the developing roller, such a warp or deformation frequently occurs, and then, it is difficult to obtain proper performances of the toner antiscattering member.
In the further example of the above-mentioned development device, since the toner antiscattering member is attached outside the development device, when the toner accumulated inside the toner antiscattering member drops by oscillation or airflow while the developing roller is driven, the toner is easily moved to the photosensitive drum, thereby causing the image defects. Thus, in a case where the toner antiscattering member is provided outside the development device, in the connection and disconnection process of the development device, there is a possibility that the toner antiscattering member comes into contact with the photosensitive drum.
Furthermore, in a case where the development device is configured to house the developing roller and the toner antiscattering member is provided adjacent to the developing roller, in particular, the toner antiscattering member is provided inside the housing, when the developing roller is housed inside the housing, the developing roller is brought into contact with the toner antiscattering member. In shipping such a development device by a ship or the like, if environment, such as temperature and humidity, is greatly changed in the shipping route, there is a possibility that the products caused by the deterioration of the toner antiscattering member, the bleeding or the like may adhere to the developing roller and that the toner antiscattering member or the developing roller may be damaged by friction, because the developing roller comes into contact with the toner antiscattering member.
In order to prevent the developing roller from being brought into contact with the toner antiscattering member when the developing roller is housed, in a case where the toner antiscattering member is formed in a short shape or a thin shape, an extra forming process becomes necessary in the producing process of the toner antiscattering member. Further, since a gap between the toner antiscattering member and developing roller becomes wider, restrain effects for scattering the toner are impaired.